Author: ["John D. Nguyen","Erica M. D'Amato","Jagan M. R. Narayanam","Corey R. J. Stephenson"]
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Abstract
Radical reactions are a powerful class of chemical transformations. However, the formation of radical species to initiate these reactions has often required the use of stoichiometric amounts of toxic reagents, such as tributyltin hydride. Recently, the use of visible-light-mediated photoredox catalysis to generate radical species has become popular, but the scope of these radical precursors has been limited. Here, we describe the identification of reaction conditions under which photocatalysts such as fac-Ir(ppy)3 can be utilized to form radicals from unactivated alkyl, alkenyl and aryl iodides. The generated radicals undergo reduction via hydrogen atom abstraction or reductive cyclization. The reaction protocol utilizes only inexpensive reagents, occurs under mild reaction conditions, and shows exceptional functional group tolerance. Reaction efficiency is maintained upon scale-up and decreased catalyst loading, and the reaction time can be significantly shortened when the reaction is performed in a flow reactor. Visible-light-mediated photocatalytic generation of carbon-centred radicals from alkyl, alkenyl and aryl iodides, which then undergo subsequent hydrogen-atom abstraction or reductive cyclizations, is reported. The protocol is characterized by the use of inexpensive reagents, mild conditions, exceptional functional group tolerance, and good to high yields.Cite this article
Nguyen, J., D'Amato, E., Narayanam, J. et al. Engaging unactivated alkyl, alkenyl and aryl iodides in visible-light-mediated free radical reactions. Nature Chem 4, 854–859 (2012). https://doi.org/10.1038/nchem.1452 